Method of making apertured film fabrics

ABSTRACT

An apertured thermoplastic fabric is formed by extruding, in the form of a film, a molten thermoplastic polymer having a secant modulus of no greater than 50,000 psi, embossing the film in a nip provided between a smooth surfaced roll and a patterned roll, wherein the patterned roll includes a plurality of discrete, raised projections disposed in a pattern and each of which includes a sharp distal end; applying sufficient pressure at the nip of the patterned and smooth surfaced rolls for causing a plurality of small apertures to be formed in the extruded film in substantially the same pattern as the pattern of discrete, raised projections; orienting the apertured film in both the cross-machine direction and in the machine-direction, and thereafter embossing the oriented film on at least one surface with a plurality of raised members spaced closer to each other than the spaces between the apertures in the oriented film, to thereby provide a matte-type finish on at least one surface. The formed fabric also forms a part of the present invention.

RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.07/720,543, filed on Jun. 25, 1991, and now U.S. Pat. No. 5,207,962,entitled "Method of Making Apertured Film Fabrics and Fabrics MadeThereby."

FIELD OF THE INVENTION

This invention relates generally to a process of fabricating anapertured film fabric and to the fabric prepared thereby. In particular,this invention relates to a process of forming an extruded, aperturedfilm having a generally cloth-like appearance and "hand", rendering ithighly desirable for use in a variety of applications wherein fibrous,woven and non-woven fabrics have been employed in the past, e.g., facingsheets for absorbent sanitary products such as sanitary napkins,incontinent pads, and the like.

BACKGROUND OF THE INVENTION

It is well known to fabricate apertured thermoplastic webs for a varietyof applications, and the prior art is replete with disclosures relatingto such webs and to processes for making them. However, most of theprior art apertured thermoplastic webs lack the desired appearance andhand to make them suitable for use as a facing sheet for sanitaryproducts (e.g., sanitary napkins and incontinent pads), as well as for avariety of other applications wherein substantially cloth-likeproperties are desired and/or required.

In a substantial number of processes high density polyethylene,polypropylene, and other high modulus, crystalline polymers have beenformed into plastic sheets, and then embossed with a variety of patternsdesigned to form thin areas in such sheets. These sheets, subsequent toembossing, are oriented either uniaxially or biaxially to cause thecrystalline web to actually open up, or fracture, into a network ofapertures in the thinned regions. Representative patents disclosing sucha process are U.S. Pat. Nos. 3,914,365; 3,441,638; 3,488,415; 4,075,379;3,922,329; 4,207,375; 4,186,781; 4,274,251; and 4,568,596.

In U.S. Pat. No. 3,386,876, Wyckoff discloses a process formanufacturing an apertured, thermoplastic web in which the apertures aredefined by a plurality of uniaxially drawn strands which are separatedfrom each other by undrawn portions. One approach to initially formingthe apertures before stretching the film is to punch the apertures intothe web in a repeating, hexagonal pattern.

As is shown in FIG. 10 of the Wyckoff '876 patent, the biaxiallyoriented web, which initially is formed with a hexagonal pattern ofapertures, has a plurality of spoke-like, uniaxially drawn strandsemanating from a central undrawn hub portion, and terminating at theiropposite ends in similar undrawn portions. Wyckoff's structures aredisclosed as being made from polypropylene, not from low density orultra low density polyethylene or other low crystallinity polymers. Aswill be seen from the description of the present invention, thestructure achieved in the Wyckoff patent is not desired in the presentinvention, and indeed would not be formed in the polymeric materialsemployed in the present invention.

In order to form apertured thermoplastic films or webs which closelysimulate in appearance and hand fibrous non-woven and woven fabrics,applicants have recognized that the thermoplastic films should beextruded from softer (i.e., lower secant modulus) polymers than theprior art crystalline polymers employed in connection with the abovediscussed prior art processes. However, processing these softer, lowcrystallinity polymers to form apertured thermoplastic films simulatingin appearance and hand the properties of conventional fibrous non-wovenand woven fabrics has not been an easily attainable objective.

In particular, applicants discovered that a number of embossing patternsand arrangements which successfully have been employed to form aperturedthermoplastic webs from high density polyethylene and other highcrystallinity polymers do not form a desirable apertured structure inlower crystallinity polymers. In particular, applicant discovered thatthinned regions formed in soft, low crystallinity polymers do not tendto open up into apertures in a predictable manner, when the extrudedpolymer films are either uniaxially or biaxially oriented.

In U.S. Pat. No. 4,842,794, the present inventors disclose a unique,two-sided embossing arrangement which, unlike prior art, single-sidedembossing arrangements, can be effectively utilized to form an aperturedfilm from soft, non-crystalline polymers. In accordance with theteachings of '794 patent the two-sided embossing pattern actually formedslits through the web during melt embossing, and the film issubsequently biaxially stretched to open up the slit regions into apattern of defined apertures. In other words, prior to the instantinvention applicants determined that the specific two-sided embossingarrangement disclosed in the '794 patent functioned to actually slit theextruded polymer film, thereby making it possible to enlarge the slitsinto apertures by the subsequent step of biaxially orienting the film.

There is absolutely no suggestion in the '794 patent that single-sidedembossing (e.g., pattern roll against smooth surface roll) could beemployed to form an apertured web in polymers having a secant modulusless than 50,000 psi. In fact, applicants' prior experience withsingle-sided embossing arrangements, in connection with the processingof high density polyethylene webs, was that thinned (not slit) regionswere formed, and that such thinned regions actually cracked, orfractured, to form a defined pattern of apertures when the extruded filmwas either uniaxially or biaxially oriented. However, prior to theinvention forming the subject matter of the present application,applicants also had determined that thinned regions formed in soft, verylow density polyethylene (e.g., Union Carbide DFDA 1137) by the use ofsome of the same embossing patterns employed to form thinned regions inhigh density polyethylene webs, did not crack and form apertures uponsubsequent biaxial orientation on the processing equipment operated andowned by applicant's assignee.

Although an apertured fabric can be formed from extruded low densitypolyethylene employing the two-sided embossing arrangement disclosed inthe Hovis et al. '794 patent, that product tended to have a number ofstrand-like polymer sections projecting in multiple planes, providing anundesired tactile feel to the product.

Thus, prior to the present invention, the prior art suggested thatsingle-sided embossing patterns employed to form thin regions inextruded, crystalline polymers would form the same type of thin regionsin softer, low-density, very low density and ultra low densitypolyethylene or other low crystallinity polymers. Moreover, although thethinned regions in the highly crystalline polymers opened into apertureswhen the film was either uniaxially or biaxially oriented, prior artthinking was that such thinned regions formed in the aforementionedsofter, low crystallinity polymers would not (and in fact did not), withany degree of predictability, open up into an apertured fabric uponuniaxial or biaxial orientation.

In fact, prior to this invention applicants believed that in order toform apertured webs from soft, low density, very low density and ultralow density polyethylene or other low crystallinity polymers, themolten, extruded film needed to be embossed by opposed patterned rolls(i.e., two-sided embossing) of the type disclosed in the Hovis et al.'794 patent. As indicated earlier, although the use of opposed patternedrolls does successfully form a defined apertured pattern in low densityand very low density polyethylene film, the three-dimensional,strand-like configuration imparted to the film has been perceived to beundesirable for a number of applications, including use as a facingsheet for sanitary absorbent products, such as sanitary napkins andincontinent pads.

OBJECTS OF THE INVENTION

Accordingly, it is a general object of this invention to provide aprocess for preparing an apertured thermoplastic film having atextile-like appearance, softness and hand.

It is a further object of this invention to provide a process forpreparing an apertured thermoplastic film having an appearance, softnessand hand making it well suited for use as a porous cover sheet forsanitary products, such as sanitary napkins and incontinent pads.

It is still a further object of this invention to provide a process forpreparing a soft and tough apertured thermoplastic film having anaesthetically pleasing apertured configuration.

SUMMARY OF THE INVENTION

The above and other objects of the present invention are achieved in aprocess for preparing an apertured thermoplastic film by extruding, inthe machine direction, a film from a molten thermoplastic polymer havinga secant modulus, in the range of 1%-2% strain, of no greater than50,000 psi, as determined either by ASTM D790-86 or ASTM D882-83.Thereafter, the extruded film is passed through the nip of two metalrollers, one of which has a substantially smooth surface and the otherof which includes a plurality of discrete, raised projections disposedin a pattern, with each of the projections terminating in a sharp distalend. The distal ends of the projections are spaced apart from each otherin both the axial and circumferential directions of the roller, andsufficient pressure is applied at the nip of the patterned and smoothsurfaced rollers for causing a plurality of small spaced-apart aperturesto be formed in the extruded film in substantially the same pattern asthe pattern of discrete, raised projections of the patterned roller.Thereafter, the apertured film is oriented in both the cross machinedirection and the machine direction, either sequentially orsimultaneously, to increase the open area of the apertures andstrengthen the film, with the film being substantially planar and beingfree of continuous strand-like sections. Thereafter, with the web at atemperature below its melt temperature, the oriented film is providedwith a micro-matte finish by directing the film through an embossing nipprovided by a patterned roll and a smooth surface roll. The patternedroll is provided with a plurality of raised regions spaced closer toeach other than the spaces between the apertures in the oriented film,to thereby provide a matte-like finish on at least one surface of thefilm.

In the most preferred embodiment of this invention the discrete raisedprojections providing apertures in the film are in the form of sharpcones which are disposed in a repeating, regular geometric pattern. Mostpreferably the repeating pattern is hexagonal.

In the most preferred embodiment of the process the extruded film isextruded from a polymer having a secant modulus in the range of 1%-2%strain, of no more than 20,000 psi, as determined either by ASTM D790-86or ASTM D882-83. Most preferably the polymer is an ultra low densitypolyethylene/octene copolymer.

All references to "secant modulus" in this application refers to thesecant modulus anywhere in the range of 1%-2% strain, as determined inboth the machine direction and cross-machine direction on a one (1) milblown film under ambient conditions (i.e., nominally 70° F. and 50%humidity) employing either ASTM D882-83 or D790-86.

Apertured film fabrics of this invention are well suited for use asfacing sheets for absorbent sanitary products of the type that generallyinclude an absorbent central core made from fluff or other well knownabsorbent material, and a moisture impervious plastic back sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other attendant advantages of this invention will becomereadily apparent from the detail description which follows when taken inconjunction with the following drawings wherein:

FIG. 1 is a fragmentary plan view illustrating the apertured web made inaccordance with the process of this invention;

FIG. 2 is an enlarged view of the circled section of FIG. 1, showingdetails of construction of the apertured web formed in accordance, withthis invention;

FIGS. 3A through 3D schematically show a continuous manufacturing linefor carrying out the process of the present invention;

FIG. 4 is a fragmentary plan view showing the manner in which the web ofthe invention is stretched in the cross-machine direction in the portionof the apparatus shown in FIG. 3B;

FIG. 5 is a partial plan view of the embossing roll employed to formapertures in the film, in accordance with the process of this invention;

FIG. 6 is a sectional view taken along line 6--6 of FIG. 5;

FIG. 7 is a partial plan view of the embossing roll employed to form thematte finish in the apertured web; and

FIG. 8 is a photograph at 25X magnification of a portion of the uppersurface of the web made in accordance with the process of thisinvention.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 3A, a molten, thermoplastic web 10 is extruded througha die 12 of a conventional extruder 14. The thermoplastic polymer,details of which will be described later, has a melting point ofapproximately 115° C., and the die 12 is maintained at a temperature inthe range of about 240° C. to about 250° C., at its exit end.

As can be seen in FIG. 3A, the web 10 exits the die in a substantiallyvertical orientation and immediately enters the nip 16 provided betweena patterned, metal embossing roll 18 and a smooth surfaced, metal backuproll 20. In accordance with this invention both the embossing roll andthe backup roll preferably are maintained at a temperature in the rangeof between 20° C.-70° C., and most preferably at approximately 45° C.Moreover, it has been determined that the smooth surface of the backuproll 20 should be formed with a crown, i.e., if should be provided witha convex curvature in the axial direction. In an exemplary embodimentthe roll 20 is provided with a curvature such that the radius of theroll on the center is approximately 4 mils greater than the radius ofthe roll at each axial end. Providing a crown on the roll has beendetermined to be desirable to compensate for flexing of the rolls, whichoccurs during embossing. It may be possible to eliminate the crowning ofthe roll 20 by increasing the size of both rolls so that they do notflex.

The embossed web 10 passes about the periphery of the smooth surfacedbackup roll 20 and is directed through a predraw unit 30. This predrawunit is shown schematically as including four smooth surfaced metalrolls 32, 34, 36 and 38. However, the number of rolls employed does notconstitute a limitation on the broadest aspects of the presentinvention.

In the most preferred embodiment of the invention the most upstream roll32 in the predraw unit 30 is driven at a rotational speed ofapproximately 70 feet/minute, and each of the following rolls 34, 36 and38 is driven at a rotational speed approximately one foot per minutefaster than the immediately preceding roll; resulting in the web 10being stretched approximately 6% in the machine direction. The primarypurpose of the predraw unit is not necessarily to stretch the web, butrather to maintain tension on the web to control the process.

Referring to FIGS. 3B and 4, the web 10 is directed from the predrawunit 30 into a tenter unit 40, in which the web is stretched in thecross-machine direction. As is illustrated in FIG. 3B, the tenter unit40 is provided with three heated zones 42, 44 and 46, located betweenthe entrance 48 and exit 49 thereof.

In accordance with a preferred form of this invention the overall lengthof the tenter unit 40 is approximately 45 feet. The web 10 enters thisunit with a cross-machine direction width of 23 inches, and exits theunit with a cross-machine direction width of 60 inches. Thus, the web 10is stretched approximately 2.6 times of its entrance width(approximately 260%) between the entrance 48 and the exit 49 of thetenter unit 40. It should be noted that the tenter unit 40 is aconventional unit sold by Marshall and Williams in Rhode Island, andincludes opposed, transversely spaced-apart chain-driven rows ofclamping jaws (not shown) which are designed to automatically clamp thelongitudinally extending edges of the web 10, as the web enters thetenter section at entrance 48. These jaws, as they are being moved inthe machine-direction, are directed transversely away from each other inthe cross-machine direction to transversely stretch the web 10, as isillustrated in FIG. 4.

Referring to FIG. 3C, after the web 10 has been stretched in thecross-machine direction in the tenter unit 40 it is directed into amachine direction stretcher unit 50. This latter stretcher unit includesan entrance section 52, an idler section 54 and an exit section 56.

The entrance section 52 includes two large driven rolls 58 and 60 (e.g.,10 inches in diameter), which preferably are driven at a speed in therange of approximately 75-78 feet per minute, which is the speed atwhich the web 10 exits the tenter section 40 at 49.

It should be noted that a small diameter roll 62 engages driven roller58 to define a drive nip 64 at the entrance section 52, to therebypositively move the web into the stretcher unit 50 at the desiredentrance speed. In a preferred embodiment of this invention the rollers58 and 60 are driven at approximately 76 feet per minute.

Still referring to FIG. 3C, the exit section 56 includes a plurality oflarge diameter, driven rolls, four of which are illustrated at 70, 72,74 and 76. The most downstream driven roll 76 engages roll 78 to definea nip therebetween, for controlling the exit speed of the web 10. Inaccordance with a preferred embodiment of this invention the speed ofthe driven rolls 70, 72, 74 and 76 is in the range of approximately130-140 feet per minute.

Located between the entrance section 52 and exit section 56 is the idlersection 54. This idler section includes a plurality of idler(non-driven) rolls which are separated from each other, but spaced closetogether. The number of idler rolls can be varied in accordance withthis invention, with the number of idler rolls utilized in an exemplaryembodiment being eleven (11).

In the illustrated embodiment the stretcher unit 50 includes fourdistinct and separated heated zones. Most preferably each of the heatedzones is at a temperature slightly less than the melt point of thepolymer.

Referring to FIG. 3, in the illustrated embodiment of this invention therolls in the entrance section 52 and the most upstream idler roll of theidler section 54 are maintained at a temperature of approximately 106°C. The idler section 54 is provided with a set of 4 (or 5) idler rollsdownstream of the first idler roll, which are heated to a temperature ofapproximately 106° C., and an immediately subsequent, or furtherdownstream set of 5 (or 4) idler rolls, which are maintained at atemperature of approximately 103° C. This latter set of idler rolls isfollowed by a single idler roll and the rolls in exit section 56, whichpreferably are maintained at a temperature of approximately 100° C. Fromthe above explanation it should be noted that the web 10 is graduallyreduced in temperature as it is directed through stretcher unit 50.

In an alternative embodiment of a machine-direction stretcher unit (notillustrated) only three distinct and separate heated zones are provided.In this embodiment the entrance section and idler section include theidentical roll arrangement as entrance section 52 and idler section 54of the machine direction stretcher unit 50. However, the rolls in theentrance section and the most upstream idler roll of the idler sectionin the alternate embodiment of this invention are maintained at atemperature of approximately 103°-104° C., as opposed to 106° C. Thefirst set of four (4) or five (5) idler rolls downstream of the firstidler roll are heated to a temperature of approximately 105°-106° C.(substantially the same as in the stretcher unit 50); however, thefurther downstream set of five (or four) idler rolls are maintained at atemperature of approximately 109° C. (as opposed to 103° C. in thestretcher unit 50). Unlike the stretcher unit 50, the alternatestretcher unit does not include a single idler roll following the secondset of five (or four) idler rolls, and does not include a separate exitsection 56.

In accordance with the exemplary embodiment of this invention employingstretcher unit 50, wherein the driven rolls 58 and 60 at the entrancesection 52 are maintained at a speed of approximately 76 feet per minuteand the driven rolls 70 and 72 at the exit section 56 are maintained ata speed of approximately 120-130 feet per minute, the stretcher unit 50stretches the web 10 approximately 158%-171% in the machine direction.

Referring to FIG. 3D, after the apertured web 10 exits the stretcherunit 50 it is directed into a texturizer and winder section 90. In theillustrated embodiment the stretcher unit 50 is shown as a continuousextension of the web forming line, and includes a driven metal patternroll 92 forming a nip 94 with a smooth surfaced, resilient backup roll96. The backup roll 92 preferably is a metal roll coated with a rubber,plastic or paper, and is selected to reduce the gloss of the web. Apreferred roll presently under consideration is made from a syntheticpolymer, identified as Supertex by Beloit Corporation of Kalamazoo,Mich. Beloit will not reveal any details relating to the chemistry ofSupertex. Most preferably the pattern roll 92 is temperature controlledto a temperature that is dependent upon a number of factors, includingits speed of rotation, its diameter and the pressure at nip 94, with thetemperature being selected to reduce gloss in the formed web.

In the present practiced embodiments of this invention the texturizerand winder section 90 is an off-line unit, adapted to receive the filmafter it has been wound into a roll form from the machine directionstretcher unit 50. In this off-line unit the pattern roll 92 is 12inches in diameter, is run at 200-400 feet per minute, is loaded toapply a pressure of approximately 1,600 pounds per lineal inch at thenip 94, and is not heated.

The backup roll 96, in an exemplary embodiment of the invention, isapproximately 16 inches in diameter, and preferably is temperaturecontrolled to a temperature of approximately 100° F. However, when thebackup roll is made of Supertex it may maintain a desired temperaturewithout the use of any special temperature control equipment.

It should be understood that the texturizer and winder section 90 can beincluded in line with the remainder of the film forming system, as isillustrated in the drawings. Whether the texturizer and winder section90 is provided as part of the continuous film forming operation will bedetermined by the economics of making the line, as opposed to theability to form acceptable apertured web structures in accordance withthe present invention.

In view of the fact that the web is not heated during the texturizingoperation applicant has determined that it is not necessary to provideany subsequent cooling operation. Accordingly, in the preferredembodiment of this invention the completed web is wound into acontinuous roll form, immediately after leaving the texturizer andwinder section 90.

However, it should be understood that in the event it is necessary toheat the pattern roll and/or back up roll to effect texturizing, thepatterned roll can be followed by a cooling roll 98, which will bemaintained at a suitable temperature to set the web prior to the webbeing directed over guide rolls 100 and 102, and then on to a drivenwinder roll 104.

A very important feature of the process of this invention resides in thecombination or selection of the proper embossing pattern and the properthermoplastic polymer composition. In fact, applicants have determinedthat utilizing the same embossing roll pattern on molten film made fromdifferent polymers does not necessarily provide or form the same patternof apertures in the completed web. In fact, grossly varyingconfigurations have been achieved with the same embossing roll pattern,merely by employing the embossing pattern on different polymercompositions.

For example, the most preferred configuration of the embossing patternof pattern roll 18 has been used in the past in connection with thefabrication of apertured webs formed from highly crystalline, highsecant modulus thermoplastic polymers, such as high densitypolyethylene. When used with these latter polymers the embossing patternof projections on the roll 18 (which will be described in detailhereinafter) merely formed thinned areas in the molten film, rather thanapertures therethrough. Upon subsequent stretching in the machine andcross-machine directions, the thinned regions opened up or fractured,providing a plurality of strand-like segments extending radially fromcentral, substantially unstretched boss regions and terminating at theiropposed ends in similar unstretched boss regions. As will be explainedlater in this application, the pattern and arrangement of apertured andunapertured sections in webs formed in accordance with this inventionare materially different from the above prior art structure.

From the above explanation it should be noted that the prior artproducts made with the embossing pattern of pattern roll 18 includedboth stretched and unstretched regions, providing a variation inproperties throughout the machine and cross-machine direction of theweb. In addition, the location of strand-like sections in multipleplanes provided a surface feel or hand which has been perceived as beingundesirable for facing sheet cover stock for sanitary napkins andsimilar absorbent products.

Turning now to FIGS. 5 and 6, the configuration of the embossing roll 18will now be described in detail. Specifically, the embossing rollpattern includes a plurality of discrete cones 200 arranged in arepeating, hexagonal pattern, as is illustrated by phantom lines in FIG.5. However, other geometric patterns may be usable in this invention.

In the most preferred form of this invention the height of the cones isapproximately equal to or slightly greater than 0.0105 inches, and thediameter of each cone, at the base thereof, is approximately 0.023inches, with the bases of adjacent cones being in engagement with eachother.

As can be seen best in FIG. 5 phantom lines 202a and 202b, whichinterconnect adjacent cones forming part of each hexagon, are parallelto each other and extend substantially perpendicular to thecircumferential direction (i.e., machine direction) of the roller. Mostpreferably the circumferential spacing between adjacent phantom lines202a and 202b is approximately 0.040 inches, resulting in a repeatingpattern of approximately 25 hexagons per linear inch in thecircumferential direction around the roll.

In accordance with broader aspects of this invention the projections aredisposed in a regular geometric pattern (most preferably hexagonal) thatrepeats less than 50 times per inch in the circumferential directionaround the roll; more preferably less than 35 per inch, and even morepreferably no more than 25 per inch. In the preferred form of thisinvention the concentration of projections is such that the geometricpattern repeats 25-35 times per inch in the circumferential directionaround the roll.

In accordance with this invention the hexagonal pattern of cones can bearranged such that the cones interconnected by phantom lines 202a and202b are aligned in the circumferential direction around the roll 18,i.e., perpendicular to the axis of said roll. In other words, thehexagonal pattern can be reoriented 90 degrees from the positionillustrated in the drawings. When the hexagons are reoriented such thatthe phantom lines 202a and 202b each are oriented in the circumferentialdirection around the roll, then the concentration of repeating hexagonsreferred to earlier will be in the axial direction along the roll, asopposed to the circumferential direction around the roll. It should beunderstood that when other geometric patterns of cones are provided theylikewise may be reoriented 90 degrees, whereby the concentration of therepeating pattern will be in the axial, as opposed to thecircumferential direction around the roll.

As was stated earlier, an extremely important feature of the presentinvention resides in the composition of the thermoplastic polymer web 10employed in conjunction with the embossing roll 18.

In the most preferred embodiment of this invention the thermoplasticfilm is formed from a polymer having a 2% secant modulus no greater than50,000 psi. This is in distinction to the prior art, high densitypolyethylene compositions, which have a 2% secant modulus in excess of100,000 psi. In the preferred embodiments of this invention thethermoplastic film is made from a polymer selected from the groupconsisting of low density polyethylene, low density polyethylenecopolymers (such as ethylene vinyl-acetate, ethylene butyl acrylate,ethylene methyl acrylate, ethylene ethyl acrylate, ethylene methylmethacrylate, ethylene acrylic acid, ethylene methacrylic acid, orethylenic ionomers), linear low density polyethylene, very low densitypolyethylene, ultra low density polyethylene, or blends of polymers inwhich the major component is low density polyethylene, low densitypolyethylene copolymers, linear low density polyethylene, very lowdensity polyethylene, ultra low density polyethylene, or theabove-mentioned polymers and polymer blends containing pigments orprocessing aids.

In the most preferred form of this invention the thermoplastic film ismade from an ultra low modulus thermoplastic polymer having a 2% secantmodulus of no more than 20,000 psi, and most preferably is an ultra lowdensity polyethylene/ octene copolymer sold under the tradename Attane4701 by the Dow Chemical Company of Midland, Mich. This polymer is anextremely tough polymer having a melt index of 1 gram/10 min, asdetermined by ASTM test method D-1238E. The density of this polymer isapproximately 0.913, as determined by ASTM test method D-792. The abovepreferred polyethylene/octene copolymer includes slip and anti-blockadditives and a phosphonite secondary antioxidant.

Added to the preferred ultra low density polyethylene/octene copolymerof this invention is a fluoropolymer copolymer lubricant to enhanceprocessibility. A preferred lubricant employed in this invention isAmpacet 10562, manufactured by Ampacet Corporation of Tarrytown, N.Y.

Also added to the composition is a whitening agent or concentrate suchas one employing titanium dioxide (TiO₂). In a preferred embodiment ofthe invention the whitening agent employed is Ampacet 41914. This agent,which is utilized in the form of a master batch, includes 50% lowdensity polyethylene, 50% titanium dioxide, less than 1% aluminumstearate (a lubricating agent) and 200 parts/million of Irganox 1010 (anantioxidant).

Another additive to the composition is calcium carbonate (CaCo₃), whichis added as a filler. In a preferred embodiment of this invention thecalcium carbonate is part of a master batch, sold under the designationAmpacet 11147. This product includes 50% calcium carbonate, and 50% lowdensity polyethylene as a carrier for the calcium carbonate.

Referring to FIGS. 1, 2 and 8 the unique web construction formed inaccordance with this invention is illustrated. Specifically, the web 10is a substantially planar, film-like member having a thicknesspreferably in the range of from about 1.5 mils to 4.5 mils, morepreferably in the range of 1.5 mils and 3.0 mils, and most preferablyapproximately 2.5 mils. The web includes a plurality of film-like areas206 (as opposed to thin strand-like sections disposed in differentplanes) which are interrupted by a plurality of apertures 208 disposedin a hexagonal array. Each of the apertures 208 has a substantialelliptical configuration formed by a substantially smooth continuouscurved surface free of sharp edges. Located in at least the uppersurface of the film-like areas is a micro-texturizing pattern which isprovided by the earlier identified pattern roll 92. As can be seen inFIGS. 2 and 8, this pattern includes a plurality of compressed, linearlines that are spaced closer to each other than the spaces between theapertures in the oriented film, to thereby provide the micro matte-typefinish. Specifically, this matte-type finish includes two separate setsof compressed parallel lines 210 and 212, which are formed by a seriesof raised, linear ribs 210a and 212a, respectively, formed on thesurface of pattern roll 92 (see FIG. 7). The spacing between the lines210 and between the lines 212 measured from center to center, is in therange of 3-10 mils, and most preferably is 6.7 mils. As can easily beseen in FIGS. 2 and 8, the sets of compressed lines 210 and 212 formedin the web 10 intersect each other, with each set of lines 210 and 212being disposed at an acute angle to the machine-direction of webformation to form diamond-shape bosses 214 in the web. By employing thetexturizing, embossing operation the film-like areas between aperturesare provided with a more textile-like "hand" and appearance (e.g., lowergloss) than would be obtained without such an operation.

Without further elaboration the foregoing will so fully illustrate ourinvention that others may, by applying current or future knowledge adoptthe same for use under various conditions of service.

What we claim as the invention is the following:
 1. A process for thepreparation of an apertured thermoplastic fabric comprising the stepsof:(a) extruding, in the machine direction, a film from a moltenthermoplastic polymer having a secant modulus of no greater than 50,000psi; (b) passing the molten, extruded film in the machine directionthrough the nip of two metal rollers, one of said rollers having asubstantially smooth surface and the other of said rollers including aplurality of discrete, raised projections disposed in a pattern, witheach of said projections terminating in a sharp distal end, said distalends of said projections being separated from each other and beingcompletely surrounded by continuous, surface regions located proximallyof said distal ends; (c) applying sufficient pressure at the nip forcausing a plurality of small apertures to be formed in the extruded filmin substantially the same pattern as the pattern of discrete, raisedprojections of said other of said rollers; (d) orienting said aperturedfilm in both the cross-machine direction and in the machine-direction toincrease the open area of said apertures, said oriented film, with theapertures formed therein, being substantially planar and being free ofcontinuous strand-like sections disposed in different planes; and (e)embossing the oriented film on at least one surface with a plurality ofraised members spaced closer to each other than the spaces between theapertures in the oriented film to thereby provide a matte-type finish onsaid at least one surface.
 2. The process of claim 1, wherein the secantmodulus of the polymer from which the film is extruded is no more thanabout 20,000 psi.
 3. The process of claim 1, wherein the thermoplasticpolymer is selected from the group consisting of low densitypolyethylene, low density polyethylene copolymers, linear low densitypolyethylene, very low density polyethylene, ultra low densitypolyethylene, and blends thereof.
 4. The process of claim 1 wherein thethermoplastic polymer includes blends of polymers in which the majorcomponent is selected from the group consisting of low densitypolyethylene, low density polyethylene copolymers, linear low densitypolyethylene, very low density polyethylene and ultra low densitypolyethylene.
 5. The process of claim 3 wherein the thermoplasticpolymer includes pigments or processing aids.
 6. The process of claim 1wherein the thermoplastic film is formed primarily from an ultra lowdensity polyethylene/octene copolymer having a secant modulus of no morethan 20,000 psi.
 7. The process of claim 1 wherein said discrete raisedprojections on the other of said rollers are disposed in a hexagonalpattern, and the concentration of said projections in one of saidmachine direction and cross machine direction is such that the hexagonalpattern repeats less than 50 times per inch.
 8. The process of claim 1wherein said discrete raised projections on the other of said rollersare disposed in a hexagonal pattern, and the concentration of saidprojections in one of said machine direction and cross machine directionis such that the hexagonal pattern repeats less than 35 times per inch.9. The process of claim 6, wherein the concentration of said projectionsis such that the hexagonal pattern repeats no more than 25 times perinch in one of said machine direction and cross machine direction. 10.The process of claim 6, wherein the concentration of said projections issuch that the hexagonal pattern repeats in the range of 25 to 35 timesper inch in one of said machine direction and cross machine direction.11. The process of claim 8, wherein the concentration of saidprojections is such that the hexagonal pattern repeats 25 times per inchin one of said machine direction and cross machine direction.
 12. Theprocess of claim 1 wherein said discrete raised projections on the otherof said rollers are disposed in a regular geometric pattern, and theconcentration of said projections in one of said machine direction andcross machine direction is such that the regular geometric patternrepeats less than 50 times per inch.
 13. The process of claim 1 whereinsaid discrete raised projections on the other of said rollers aredisposed in a regular geometric pattern, and the concentration of saidprojections in one of said machine direction and cross machine directionis such that the regular geometric pattern repeats less than 35 timesper inch.
 14. The process of claim 13, wherein the concentration of saidprojections is such that the regular geometric pattern repeats no morethan 25 times per inch in one of said machine direction and crossmachine direction.
 15. The process of claim 13, wherein theconcentration of said projections is such that the regular geometricpattern repeats in the range of 25 to 35 times per inch in one of saidmachine direction and cross machine direction.
 16. The process of claim15, wherein the concentration of said projections is such that theregular geometric pattern repeats 25 times per inch in one of saidmachine direction and cross machine direction.
 17. The process of claim1, wherein the discrete projections are substantially cone-shaped, andform a plurality of small apertures, each of which is defined by asubstantially smooth, continuous curved surface free of sharp edges whenthe film is oriented in both the machine direction and the cross machinedirection.
 18. The process of claim 17, wherein the thermoplastic filmis selected from the group consisting of low density polyethylene, lowdensity polyethylene copolymers, linear low density polyethylene, verylow density polyethylene, ultra low density polyethylene and blendsthereof.
 19. The process of claim 18 wherein the thermoplastic polymerincludes blends of polymers in which the major component is selectedfrom the group consisting of low density polyethylene, low densitypolyethylene copolymers, linear low density polyethylene, very lowdensity polyethylene and ultra low density polyethylene.
 20. The processof claim 18 wherein the thermoplastic polymer includes pigments orprocessing aids.
 21. The process of claim 17 wherein the thermoplasticfilm is formed primarily from an ultra low density polyethylene/ octenecopolymer having a secant modulus of no more than 20,000 psi.
 22. Theprocess of claim 17 wherein said discrete raised projections on theother of said rollers are disposed in a hexagonal pattern, and theconcentration of said projections in one of said machine direction andcross machine direction is such that the hexagonal pattern repeats nomore than 35 times per inch.
 23. The process of claim 22, wherein theconcentration of said projections is such that the hexagonal patternrepeats no more than 25 times per inch in one of said machine directionand cross machine direction.
 24. The process of claim 22, wherein theconcentration of said projections is such that the hexagonal patternrepeats in the range of 25 to 35 times per inch in one of said machinedirection and cross machine direction.
 25. The process of claim 24,wherein the concentration of said projections is such that the hexagonalpattern repeats 25 times per inch in one of said machine direction andcross machine direction.